3G4 ox TWO "J^EW CBTTEllIA IT^ THE STUDY OE LTCIIEXS. 



affinity of vitellina the Lichen which I hare described under the 

 name of Placodium medians^ and which but for the reaction we 

 should have taken for a variet}^ of murorum ; but in reality JLeca- 

 nora medians is very near to L. crenata^ ^yl- {Lielien raurorum^ 

 var. crenulafus, Wlilnb. Lapp. p. 41G), and is distinguished from 

 this latter in the same way as epixanilia, Aith,^ ivora vifcUina*. 

 The species of the group of Lecanora cerina, on the other hand, 

 always exhibit the chrysophunic reaction, at least on their apo- 

 thecia and on their thalli; if these are of a yellow colour. This 

 reaction, moreover, is visible (and constantly intense) in the 

 yellow Fhyscice^ in the yellow species of Flacodiiim^ in the apo- 

 thccia of the erythrocarpous Cladonit^, in the apothecia of Leca- 

 nora ventosa, 1i(Bmatomma, erythromma, in Lecidea DomingemiSj 

 Jlavocroceay eJiri/sosticta, Iciicoxantlta^ cinnaharina^ r^issula, &e. 



Tlie potash gives also quite another reaction, that oi nsneic ana 

 lecanoric acid^ i.e. a yellow or greenish yellow (^^jaune ou jaune- 

 verdutre") reaction, and that very frequently, on the thalli of 

 Lichens. By the presence or absence of this yellow reaction, we 

 can equally distinguish many species in a manner far easier and 

 more certain than by the ordinary characters hitherto affixed to 

 them. Thus, Lecanora sulfusca exhibits the yellow reaction ; but 

 umlrina, creuulafa, conferta, do not exhibit it. 



A tliird reaction obtained wath the potash is that of which 

 Lecanora cinerea offers an example : the thallus at first becomes 

 of a yellow colour, but in less than a minute the yellow colour is 

 changed into a red colour. In gilhosa (and calcarea, lacnsfris, &e., 

 which do not differ from it except as varieties), so often difficult to 

 be distinguished from cinerea^there is no reaction with the potash. 

 The cinereo-rufescens, Anzi (Langob. 73), which exhibits the re- 

 action of cinerea^ is nothing more than a variety of cinerea (which 

 we may name ^ha-opta^, whilst the true cinereo-rtifescens and its 

 forms diamarta and olscurata are distinguished by the absence 



of all reaction with the potash. The reaction of cinerea is found 

 also in Lecanora oculata-f, but no reaction in mictalilis and ver- 

 Tiicosa. The thallus of Lecanora llanda becomes at first yellow, 



The absence of the ehrysophanic actiou is ohservable also in a great nnmher 

 of Lichens which haye yellow or orange thaUi or apothecia,— e.^. in the yellow 

 species of Tlaf^.mia, in Lecanora cTirysophtliahna, epanora, SciUicherih <^^^^^' 



carjpon, kc. 



+ In Parmelia acetahxdum the th 

 that observable in Lecanora cinerea. 



tph 



1 



I 



same 



